Materials that are responsive to changes in the conditions in a medium to which it is exposed but yet do not fall apart when subjected to such changing conditions are difficult to synthesize. These materials include a variety of polymeric materials which may use adaptive cross-linkers that can modulate the response to changes in the environment and can exhibit observable or measurable properties such as swelling when soaked in a particular liquid. For example, DNA (a special block co-polymer) is used as a reversible cross-linker in a hydrogel (hydrophilic polymers) that can modulate the mechanical and rheological properties of the hydrogel and at the same time, it can selectively bind a variety of biological molecules. Liu, Juewen, “Oligonucleotide-functionalized hydrogels as stimuli responsive materials and biosensors,” Soft Matter, 2011, 7, 6757-6767. Such properties are useful in controlled drug delivery systems, protein separations and biological sensors.
For materials that involve non-carbon based polymeric materials such as those found in ceramic types, e.g., metal oxides, few, if any, are available as responsive materials that involve conformational changes. This is especially true when it involves swelling in several media. More problematically, to successfully synthesize such materials that rely on organometals that have different moieties is not straightforward because reactivity is different for different organometals. For example as described in U.S. Utility patent application Ser. No. 12/701,862 “Method for Making High Purity Metal Oxide Particles and Materials Thereof,” which is incorporated by reference herein in its entirety, inserting titania or titanium oxide in an amorphous silica particle using condensation of the precursor organosilanes such as tetramethoxysilane or tetraisopropyl ortho titanate is not straightforward. This is due to differences in the degree of reactivity between the two. Therefore, the '862 application addressed this by balancing the feed of the silicon metal precursor versus the titanium metal precursor that prevents the premature gellation of titanium versus silicon; resulting in a single phase product rather than distinct separate titania and silicate phases.
On the other hand, organic-inorganic hybrid materials having different moieties of two different precursor sources, especially those that concerns organic moieties such as those found in several organosilanes, will have similar difficulty in successfully reacting so that one precursor is a part of the other without having both form as separate entities. These are concerns to successfully produce organic-inorganic hybrids that have special stimuli sensitivity to temperature, pH, etc. and responses such as physically swelling in a media or changes in electrical or optical characteristics, etc.